1. Technical Field
The present invention relates a screen that reflects light from a projector or any other projection apparatus disposed in front of the screen to present a projected image.
2. Related Art
There is a reflective screen known to reflect a projected image produced by upward oblique projection to allow a viewer to observe the projected image. For example, JP-A-2006-215162 describes a screen of this type in which a large number of microlenses having the same convex shape (unit shape portions) are regularly disposed on a screen substrate to form reflection surfaces only on lower portions of the microlenses so that external light from the above is blocked and high contrast is achieved.
As another known example of the screen of this type, there is a screen having a similar function in which a large number of microlenses having the same concave shape are regularly disposed on a screen substrate.
A screen in which a large number of microlenses having the same shape are regularly disposed as described above, however, has the following problems to be solved.
In a microlens-based screen of related art, the spacing between the lenses is reduced to provide brightness equivalent to that of a matted screen, which is called a white mat. However, when the spacing between the lenses is reduced to, for example, a value smaller than 0.2 mm, glaring interference fringes, which appear above the screen and are called scintillation (or speckle), are disadvantageously produced.
On the other hand, to eliminate the scintillation, it is effective to increase the spacing between the lenses. For example, when the spacing between the lenses is increased to 0.2 mm or greater, the scintillation is hardly visible to the eyes of the viewer, and hence the viewer unlikely visually recognizes the scintillation. However, the scintillation and the brightness are in a trade-off relationship; when the spacing between the lenses is increased to 0.2 mm or greater to eliminate the scintillation, a projected image will not be sufficiently bright and the screen becomes dim.
It is alternatively conceivable to increase the diameter of each of the microlenses and hence the spacing between the lenses. In this case, however, since the number of microlenses that can be incorporated in a unit area is less than the number required, the resolution decreases and a moire pattern appears. The approach described above has therefore a limitation, and the diameter of each of the lenses is at present forced to be, for example, 0.5 mm or smaller.